How to
produce cuttings (clones)

Cuttings or “clones” are a popular method of propagating plants. A cutting
is a plant part removed from a ‘donor’ or ‘mother’ plant that will develop
roots and shoots when placed in a growing medium under favourable
conditions.

1. For many species, cuttings reach the vegetative stage faster than
seedlings.
Further, cuttings taken from the most recent growth will produce plants that
take less time to reach biological maturity than cuttings taken from older growth. Commercial fruit growers use cuttings to minimise the
lengthy non-fruiting phase associated with seed propagated plants. When
artificial lighting is used, cuttings can be switched to flowering sooner by
changing to the “redder” light spectrum of a HPS lamp. This is beneficial
because the crop cycle is faster.

2. Cuttings produce a plant having the same general genetic characteristics
as the donor plant. For example, the same appearance, size and yield. The
result with seeds can be more uncertain.

Stem cuttings

The most appropriate cutting material will vary between plant species.
However, most species can be propagated using 'stem cuttings'. A stem
cutting incorporates stems, leaves and buds (Fig 17.2). Roots grow from the
basal wood (Fig 17.1) and shoots grow from the buds.

Procedure for producing cuttings

Step 1. Thoroughly sterilize all the
hardware that is likely to come in contact with the cuttings.

Step 2. Pre-soak the
growing medium (e.g. Rockwool)
by immersing or drenching with a pH buffered
seedling nutrient solution. This will
help remove the excess ‘alkalinity’ that is often present in this material.
Allow excess nutrient to drain. If using Rockwool, gently squeeze to remove
the excess nutrient.

Step 3. (Fig 17.4) To increase the
success rate of cuttings, use a ‘heat mat’ and ‘propagation lid’ to maintain
the root and air temperature at 20-25OC (68-77OF), and relative humidity at ~80% (see section on bottom
heat below). Use “cool white” fluorescent
lighting timed to run 18 hours per day. Ensure to establish this
environment prior to planting cuttings.

If cuttings are being grown outdoors, use a propagation lid and position in
a partly shaded location. Too much light in the early stages can stress
cuttings.

Step 4.Select a plant that has been
well maintained, has favourable characteristics and is free of disease. The
cutting material must be of 'semi-hard' wood i.e. stem material that is no
longer soft and supple like new growth. Avoid plants that are well into the
flowering stage.

Step 5. Using secateurs or a scalpel,
remove a 'lateral' (side branch) that has at least 3 sets of leaves (Fig
17.2). Immediately place the cut end into lukewarm water.

Step 6. Using a scalpel, trim the
cuttings as per Fig 17.3a: (1) Remove the bottom set of leaves**; (2) Re-cut
through the stem at a 45O
angle below where the lowest set of leaves were. Large leaves should be cut
in half if they tend to wilt during the first few days of planting.

Step 7. Immediately immerse region (3)
into cutting gel or powder (Fig 17.3a & 17.3b). Punch a snug hole in the
medium, deep enough to accommodate region (3). Push the cutting right to the
base of the pre-made hole then press the medium against the stem (Fig
17.3c).

Step 8. Mist cuttings daily using water
or a seedling foliar fertilizer. Water
the medium as required using a bloom nutrient solution at EC 0.3-0.8mS
(typically about one-third the normal strength). To avoid stem rot and
disease, use an anti-fungal root drench
and never allow the medium to remain waterlogged. Diligently remove any dead
leaves or dead cuttings as these are an ideal host for fungi. Also, remove
any floral buds that form.

Step 9. Depending on the plant variety,
roots usually develop within 7-10 days. Once
this occurs, gradually expose the cuttings to their proposed environment. Be
careful because a sudden change in humidity, nutrient strength, light
intensity or
temperature
might kill them. Therefore, gradually increase the nutrient strength to that
required for the vegetative phase - see
Table 11.30. Initially remove the propagation lid for ~30 minute
periods, 1-2 times per day. Then increase the frequency and duration over
the course of a few days, or as required, until the cuttings are ready to be
planted.

**If the growing medium is sufficiently deep, it is possible to get better
survival rates by having a second set of leaf “nodes” below the medium’s
surface (Fig 17.3d). When planting, position these nodes ~5mm (1/5 inch)
below the surface of the medium.

Bottom heat for cuttings

Bottom heat is highly beneficial for 'cuttings' because it increases the
respiration rate at the ‘cut’ end. The respiration rate is critical because
it produces energy to form roots.

Note, excessive air temperature is counter productive for root production in
cuttings. It increases the rate of transpiration causing cell dehydration
(i.e. there are no available roots to replace the water lost from leaves)
and increased shoot growth, which depletes carbohydrate reserves. Therefore,
avoid allowing the air temperature to exceed 25OC / 77OF.